Osteotomies for treating hallux valgus have already been known for decades and have the object of functionally reconstructing the axis of the 1st metatarsal. It is necessary in this context, after the osteotomy, to fix the two bone fragments in their corrected position in order to prevent mobility between the fragments and to permit reliable osseous union without dislocation.
To fix the osteotomy, it is already known to use plates which are secured to the cortical bone by means of a number of screws in order to prevent the bone fragments from buckling. A considerable surgical outlay is required for this.
Bone clamps are also known for fixing the osteoLomy, but their use involves the risk of splintering of the bone.
AT 937 U has disclosed an implant for fixing two bone fragments to each other, in particular for treating an axial deviation of a metatarsal bone, e.g. hallux valgus, which implant comprises a clasp with two arms which are connected to each other at one of their ends and in this area delimit an opening for passage of a screw which can be screwed into one of the two bone fragments and which, with their other, free ends, can be introduced into the medullary cavity of the other bone fragment and can spread apart. After osteotomy has been performed, the clasp is introduced proximally into the medullary cavity of one bone fragment via the free ends of the two arms and spreads apart in this medullary cavity, after which the clasp is anchored on the other bone fragment by means of the screw guided through the opening.
As a result of the spreading force and the frictional fit of the clasp arms, and as a result of the intermittent compression arising upon functional loading, the intramedullary part of this known implant has a high degree of stability. By contrast, however, the extramedullary part is anchored in the bone via only one screw, whereas a two-point bearing is required on account of the torque which increasingly occurs as the compression of the screw anchoring between implant and metatarsal head decreases.